1. Field
The following description relates generally to digital signal processing and, more particularly, to a method and apparatus for spectral sensing.
2. Background
The Federal Communications Commission (FCC) is developing rules to allow white space devices to use the TV frequency bands provided that the devices do not cause harmful interference to TV receivers. To avoid causing interference, the devices must continuously sense the environment, dynamically identify unused spectral segments (i.e., white space), and operate in the identified white space without causing interference. One essential function of white space devices is that they reliably detect weak incumbent signals at a very low signal-to-noise ratio (SNR). One technique for spectrum sensing is disclosed by Chang et al., “Spectral Correlation Sensing,” IEEE 802.22-07/0284rl, July 2007. The disclosed technique is deficient in its ability to reliably detect weak signals in practical radio systems, as the technique does not adapt to a scaling factor introduced by the automatic gain control (AGC) and/or low-noise amplifier (LNA) of the RF front-end, and in addition, does not account for a frequency offset introduced due to a mismatch between the local oscillator and the oscillator at the transmitter. As such, there is a need for an improved and practical detection technique that can reliably detect weak signals at a very low SNR.